Field of the Invention
Embodiments of the present invention generally relate to apparatus and methods for selectively oxidizing silicon.
Description of the Related Art
Oxidation of silicon is a fundamental technology to CMOS fabrication, dating back to the inception of the integrated circuit. The most common methods for oxidation of silicon rely on thermal processes in ambient of O2, H2O/H2, H2O/O2, O2/H2 or combinations thereof. The hardware used to provide the silicon oxidation process during IC manufacturing are batch thermal furnaces and RTP. In conventional oxidation systems and processes, high temperature (above 700° C.) is required to provide the activation energy for the oxide growth on silicon or poly-silicon.
Advanced integrated circuit fabrication requires a number of process steps where thin films of silicon oxide are grown on silicon or polysilicon structures. For some applications, the oxidation process must be selective, such that other materials including tungsten are not oxidized. Currently thermal processing in either an ambient of O2, H2O/H2, or H2O/O2 at high temperature (greater than 700° C.) is used to perform this oxidation processes.
The high temperatures are necessary to obtain the oxide growth rate to make the process practical and in some cases are required for oxide quality. However, many of the next generation devices will undergo serious damage at the point in the process flow where the oxide growth is required, if exposed to the combination of high temperature and an oxidizing environment. Thus, there is a need in the art for methods and apparatus which allow for low temperature selective oxidation of silicon without oxidizing other surface materials.